1. Field of the Invention
The present invention relates to a projector apparatus, a method for obtaining an inclination angle of a projector, and a method for correcting a projection image.
2. Description of the Related Art
A projector is an apparatus for displaying an image on a screen. It projects a light toward a screen and displays an image on the screen.
When the projector is not inclined with respect to the ground planar surface and the screen stands perpendicular to the ground planar surface, an image is undistortedly displayed on the screen.
However, if the projector is inclined with respect to the ground planar surface, an image on the screen is distorted. To prevent this, some conventional projectors have an acceleration sensor inside. The acceleration sensor detects the inclination angle of the projector with respect to the ground planar surface. The projector performs trapezoidal correction based on the detected inclination angle. Such a projector is disclosed in, for example, Unexamined Japanese Patent Application KOKAI Publication No. 2001-339671 page 3 and FIG. 1.
However, actually, the screen is not necessarily perpendicular to the ground planar surface.
Therefore, to determine the correction amount for trapezoidal correction, not only the inclination angle of the projector with respect to the ground planar surface, but also the inclination angle of the projector with respect to an axis that is perpendicular to the screen are needed. If these inclination angles can be measured, trapezoidal correction can be performed.
Conventional projectors correct the distorted outline of an image to a correct outline in this manner.
However, conventional projectors have the following problems.
First, as described above, inclination angles needed for trapezoidal correction of an image are an inclination angle of the projector with respect to the ground planar surface, and an inclination angle of the projector with respect to the axis that is perpendicular to the screen. Therefore, even if the inclination angle of the projector with respect to the ground planar surface is detected but if the inclination angle of the projector with respect to the screen cannot accurately be measured or the measured result cannot be supplied to the projector, trapezoidal correction cannot accurately be performed.
Second, conventional projectors employing an acceleration sensor ignore the inclination angle of the screen with respect to the projector in a direction parallel to the ground planar surface. Actually, there can possibly be an inclination angle of the screen with respect to the projector in the horizontal direction. The acceleration sensor cannot detect the inclination angle of the screen with respect to the light axis of a projected light. Therefore, conventional projectors employing an acceleration sensor cannot perform trapezoidal correction based on the inclination angle of the screen with respect to the projector in the horizontal direction.
The disclosure of the above-indicated document is incorporated herein.